Security padlock

ABSTRACT

A maximum security padlock having a shielding plate recessed and retained in the lock casing to minimize exposure of the lock&#39;&#39;s replaceable key cylinder permitting only limited access to the key slot therein. The shielding plate is dovetailed into a complementary recess in the bottom of the casing and cooperates therewith to provide a flush, crevice-free padlock closure case around the lock mechanism. A pair of retaining members secure the shielding plate in the casing and accommodate release of the plate, to replace the key cylinder, only when the lock is in an unlocked condition.

United States Patent Lippisch Sept. 17, 1974 SECURITY PADLOCK [75] Inventor: Guillermo W. Lippisch, Park Forest South, Ill.

[73] Assignee: Junkunc Bros. American Lock Company, Crete, Ill.

22 Filed: Mar. 23, 1973 21 Appl. No.: 344,193

[52] US. Cl. 70/38 A, 70/52, 70/36 B [51 Int. Cl E05b 67/02, E05b 67/22 [58] Field of Search 70/38 R, 38 A, 38 B, 38 C,

[56] References Cited UNITED STATES PATENTS 212,892 3/1879 Budd 70/52 2,930,219 3/1960 Fansmith 70/51 X 3,422,643 1/1969 Foote 70/38 B 3,713,309 1/1973 Miller 70/38 A FOREIGN PATENTS OR APPLICATIONS 528,953 7/1931 Germany 70/52 Primary Examiner-Robert L. Wolfe Attorney, Agent, or Firm Hill, Gross, Simpson, Van Santen, Steadman, Chiara & Simpson [57] ABSTRACT A maximum security padlock having a shielding plate recessed and retained in the lock casing to minimize exposure of the locks replaceable key cylinder permitting only limited access to the key slot therein. The shielding plate is dovetailed into a complementary recess in the bottom of the casing and cooperates therewith to provide a flush, crevice-free padlock closure case around the lock mechanism. A pair of retaining members secure the shielding plate in the casing and accommodate release of the plate, to replace the key cylinder, only when the lock is in an unlocked condition.

4 Claims, 4 Drawing Figures SECURITY PADLOCK BACKGROUND, SUMMARY AND ADVANTAGES OF THE INVENTION Shackle-type padlocks have been developed in the past to resist tampering and damage, and provide the utmost in security. Lock casings have been constructed of special tough alloys or have been hardened to withstand attacks of various cutting and impact tools and further, the shackles have been shielded to lessen vulnerability to intruders. Such padlocks, however, still suffer from the disadvantage that the key cylinder, formed of relatively soft brass or other similar alloys, remains exposed to the tampering devices of would-be intruders. If sufficient pry leverage is applied to the key cylinder to unseat it from the casing, the special alloys, heat treatments or shackle shielding are of little avail to provide the desired security.

Accessibility to the key cylinder in the casing of the padlock is, of course, extremely desirable in order to accommodate the changing of key cylinders having different tumbler pin combinations. Further, changing of the key cylinder is easily accomplished and without sacrificing the locks security.

In accordance with the principles of the present invention, a shielding plate, of complementary alloy or hardening with the lock casing and secured therein, underlies the key cylinder, permitting only limited access to the key slot therein. The shielding plate is dovetailed and slidably seated into a complementary recess in the bottom of the casing and cooperates therewith to provide a crevice-free casing invulnerable to prying or wedging burglary tools.

A pair of retaining members secures the slidable, shielding plate in the casing. One of said members is a set screw adapted to release the shielding plate to accommodate replacement of the key cylinder when the lock is in an unlocked condition. The second of the retaining members is a plunger, biased against a spring by one leg of the shackle into locking engagement with the shielding plate when the shackle is in a locked condition.

A principal advantage of the present invention, therefore, is the maximum security provided for a lock accommodating replacement of its key cylinder.

A further advantage of the present invention is in utilizing the dovetailed plate to retain and greatly limit exposure of the key cylinder when the padlock is in a locked condition.

A still further advantage of the present invention resides in the ease of removing the dovetailed plate to replace the key cylinder when the padlock is in an unlocked condition.

Other objects, features and advantages of the invention will be readily apparent from the following description of a preferred embodiment thereof, taken in conjunction with the accompanying drawings, although variations and modifications may be effected without departing from the spirit and scope of the novel concepts of the disclosure.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a padlock constructed in accordance with the principles of the present invention;

FIG. 2 is a transverse sectional view taken through the padlock shown in FIG. 1, showing the padlock in a locked condition;

FIG. 3 is a bottom view of the lock shown in FIG. 1, with the shielding plate removed to expose the key cylinder and the plate retaining members; and

FIG. 4 is a partial fragmentary sectional view taken substantially along the line IVIV of FIG. 2 showing the release of the retaining member from the shielding plate.

DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION In the embodiment of the invention illustrated in the drawings, I show in FIG. 1 a maximum security padlock 10 having a casing 12, preferably constructed of a material especially resistant to damaging effects of burglary tools, with built-up or extended portions l4, l4 and having a pair of parallel bores 16 and 18 therein. The bores 16 and 18 slidably receive legs 20 and 22 of a generally U-shaped shackle 24. A compression spring 26 seated on a heat 72" of a plunger 72 in the bottom of the bore 16, biases the leg 20 of the shackle 24 upward, so that the leg 22, being the shorter of the two shackle legs, can be withdrawn from the casing 12. The longer leg 20 has an annular recess 28 extending thereabout and adapted to be engaged by a retainer pin 30 for retaining the longer leg 20 in the casing 12 when the padlock 10 is unlocked.

The legs 20 and 22 also have arcuate recesses 32 and 34 in the inner facing sides thereof and adapted to be engaged by balls 36 and 38 extending from a transverse extending passageway 40. The balls 36 and 38 are engageable with the recesses 32 and 34 to lock the shackle 24 in the casing 12 when the balls 36 and 38 are in engagement with the cylindrical wall of a locking member 42 rotatably mounted in a bore 44 extending upward from the bottom of the casing 12. The cylindrical wall of the locking member 42 has diametrically opposed flattened portions 46, 46 which when registered with the balls, accommodate retraction of the balls 36 and 38 out of engagement with the arcuate recesses 32 and 34 to accommodate opening of the padlock by upward pulling movement of the shackle 24, to withdraw the shorter leg 22 from the bore 18, whereupon the leg and shackle may be rotated about the axis of the leg 20.

The extended portions 14, 14 of the casing 12 enclose the legs 20 and 22 of the shackle 24 so as to hinder attack of the shackle when in the locked position.

A standard replaceable key cylinder 48 is shown as being generally figure-8 in form and carrying a key plug 50 with a key slot 51 therein, having communication with the locking member 42, for rotatably moving said locking member to lock and unlock the padlock 10 in a manner well known to those skilled in the art, so not herein shown or described further. The key cylinder 48 is seated in a matching generally figure-8 shaped aperture or socket 52 at the bottom of the casing 12, and is retained therein by an elongated shielding plate 54, underlying the key cylinder 48. The shielding plate 54 is of a complementary alloy or hardness with the lock casing 12 and is dovetailed in configuration for seating into a complementary recess 56 fonned into the bottom of the casing 12.

The recess 56 is defined by a pair of gibs 58, 58 extending along the sides of the casing 12 and arcuately joined at an inner end of the recess 56 to form a U- shaped slot with a tapered retaining lip extending thereabout. The dovetailed shielding plate dimensions and tapered side walls 60 closely conform to the casing recess 56 so that when the shielding plate is in position in the recess 56, a flush, crevice-free casing surface 62 is provided to resist entrance of prying or wedging tools.

The dovetailed shielding plate 54 further includes upper and lower surfaces 64 and 66 and a straight end wall 68. The lower surface 66 and end wall 68 align with the casing bottom surface 62 and side wall surface 70 thereof. While the shielding plate 54 covers much of the key cylinder 48, a minimum size aperture 69 therein accommodates use of a key in the key slot 51 of the key plug 50.

Now with reference to FIG. 2, it can be seen that the shielding plate 54, when seated in the recess 56, extends from the casing side wall 70 to a location which underlies the bore 16. The shielding plate 54 also underlies the bore 18 and key cylinder socket 52 and is secured in the recess 56 by a pair of retaining members, comprising a plunger 72 having a head 72" forming a seat for the compression spring 26 in the bore 16, and by a dog point set screw 74 screwed into a threaded bore 76 at the bottom of the bore 18 and arranged to engage a bore 78 in the upper surface 64 of the plate 54. A second bore 80 in the upper surface 64, aligns with a pin projection 73 of the plunger 72 to secure the shielding plate 54 against slidable disengagement with the recess 56, whenever the shackle leg 20 is depressed into the casing 12. The plunger 72 is biased downward by the spring 26 into locking engagement with the bore 80 and is biased upward out of locking engagement by a spring 82.

Accordingly, whenever the padlock is in an unlocked condition, the spring 82 moves the plunger 72 upward out of engagement with the bore 80, against minimal compressive resistance of the spring 26 which is virtually fully extended when the annular recess 28 of the shackle leg 20 engages the retaining pin 30 at a time when the lock is open. Conversely, when the shackle leg 20 is fully depressed into the bore 16 as in the locked condition, the greater compressive force of the spring 26 overcomes the opposing biasing force of the spring 82 to move the plunger pin 73 downward into locking engagement with the bore 80.

It may now be seen that only when the padlock is in an unlocked condition with the plunger pin 73 disengaged and the shackle leg 22 withdrawn from the bore 18 and rotated about the axis of the shackle leg 20 that the second retaining member, set screw 74, is accessible at the bottom of the bore 18 to unscrew it from locking engagement with the bore 78 of the shielding plate 54, as best shown in FIG. 4. Now, with both retaining members 73 and 74 released, the plate 54 may be slid out of the recess 56 to expose the key cylinder 48, as best seen in FIG. 3, to facilitate the removal thereof from the aperture 52 of the casing 12, and accommodate replacing of the key cylinder 48 with another having different tumbler pin combinations.

it will be apparent from the foregoing that a maximum security padlock is provided without the shortcomings of prior designs, which do not adequately protect the key cylinder. Further, simple guarded release means for the shielding plate to retain the key cylinder has been provided to accommodate quick removal of the key cylinder for replacement by a different key cylinder, by merely unlocking the padlock and withdrawing the short leg 22 of the shackle from its bore 18 to gain access to the set screw 74 at the bottom of the bore 18. A tool, reaching down the bore 18, can then unscrew the set screw 74 from locking engagement with the shielding plate bore 78 to permit the plate to be slid out of the recess 56, whereupon the key cylinder may be withdrawn for replacement with another key cylinder.

I claim as my invention:

1. In a shielded padlock,

a casing having a pair of parallel bores,

a shackle having a pair of parallel legs slidably engaged in said bores,

locking means to secure said shackle in said casing when the legs are depressed into said bores,

an interchangeable means for releasing said locking means including:

a key cylinder mounted in said casing,

a key plug rotatably carried in said cylinder and having a key slot operable by turning movement of a key to release said shackle to allow one of said legs to be withdrawn from said casing,

a cover place for said key cylinder slidably received in said casing to retain said key cylinder in said casing and releasable to afford access to said key cylinder, to accommodate changing of the key cylinder to a key cylinder having a different tumbler pin combination only when the shackle is released,

a slidable interengaging connection between said cover plate and said casing extending along opposite sides and an inner end of said cover plate and providing a crevice-free, flush exterior casing surface, and

spaced retaining means releasably pocketed in mating recesses in an unexposed surface of said cover plate in alignment with said parallel legs of said shackle, to retain said cover plate to said casing and to prevent release thereof except when said shackle is released.

2. The shielded padlock of claim 1, wherein the interengaging connection is dovetailed in configuration, and wherein the retaining means retaining said cover plate in fixed engagement with said casing comprises a pair of spaced pins, each aligned with one of said shackle legs and unexposed except when said shackle is released.

3. The shielded padlock of claim 2, wherein one of said pins comprises a plunger depressible into locking engagement with one of said cover plate recesses by one of said shackle legs upon depressing the shackle into a locked condition in the casing, and wherein a second of said pins comprises a set screw, threaded into said casing and turned down into locking engagement with the other of said cover plate recesses.

4. The shielded padlock of claim 3, wherein means affording release of said retaining means includes spring biasing means for said plunger to disengage the plunger from its locking engagement with said cover plate concurrently with the release of said shackle and withdrawal of one of said shackle legs from its related casing bore to provide access to said set screw. 

1. In a shielded padlock, a casing having a pair of parallel bores, a shackle having a pair of parallel legs slidably engaged in said bores, locking means to secure said shackle in said casing when the legs are depressed into said bores, an interchangeable means for releasing said locking means including: a key cylinder mounted in said casing, a key plug rotatably carried in said cylinder and having a key slot operable bY turning movement of a key to release said shackle to allow one of said legs to be withdrawn from said casing, a cover place for said key cylinder slidably received in said casing to retain said key cylinder in said casing and releasable to afford access to said key cylinder, to accommodate changing of the key cylinder to a key cylinder having a different tumbler pin combination only when the shackle is released, a slidable interengaging connection between said cover plate and said casing extending along opposite sides and an inner end of said cover plate and providing a crevice-free, flush exterior casing surface, and spaced retaining means releasably pocketed in mating recesses in an unexposed surface of said cover plate in alignment with said parallel legs of said shackle, to retain said cover plate to said casing and to prevent release thereof except when said shackle is released.
 2. The shielded padlock of claim 1, wherein the interengaging connection is dovetailed in configuration, and wherein the retaining means retaining said cover plate in fixed engagement with said casing comprises a pair of spaced pins, each aligned with one of said shackle legs and unexposed except when said shackle is released.
 3. The shielded padlock of claim 2, wherein one of said pins comprises a plunger depressible into locking engagement with one of said cover plate recesses by one of said shackle legs upon depressing the shackle into a locked condition in the casing, and wherein a second of said pins comprises a set screw, threaded into said casing and turned down into locking engagement with the other of said cover plate recesses.
 4. The shielded padlock of claim 3, wherein means affording release of said retaining means includes spring biasing means for said plunger to disengage the plunger from its locking engagement with said cover plate concurrently with the release of said shackle and withdrawal of one of said shackle legs from its related casing bore to provide access to said set screw. 